You must install Windows Server 2003/2008 Enterprise Edition or Datacenter Edition on each primary and failover node. Each node must be running the same operating system.
Note the following restrictions:
Neither Compliance Accelerator nor Discovery Accelerator must be installed on any server in the planned cluster. These products are not supported within a cluster. However, an unclustered Compliance Accelerator or Discovery Accelerator can reference a clustered Enterprise Vault virtual server.
The Enterprise Vault Configuration wizard does not support resource groups that contain multiple network name or IP address resources.
We recommend that Enterprise Vault cluster groups contain only resources related to Enterprise Vault.
If you have an existing Enterprise Vault 7.0 or later installation then, subject to certain restrictions, you can use the Enterprise Vault Convert to Cluster wizard to convert the Enterprise Vault servers to servers with cluster support. The conversion requires you to move the Enterprise Vault data manually to highly available locations.